1. Field of the Invention
The present invention relates to a capsule toner, a two-component developer, and an image forming apparatus.
2. Description of the Related Art
In recent years, there has been interest in energy conservation and reduction of CO2 from the aspect of environmental conservation and the like.
An electrophotographic image forming apparatus is also no exception and it has been desired to reduce power consumption of the image forming apparatus by decreasing a fixation temperature of a toner onto a recording medium than in the conventional manner. Further, in order to achieve high-speed printing, reduction in fixation time and low temperature fixation have been required.
In order to realize low temperature fixation, there has been proposed a method for decreasing a flow tester softening temperature and a glass transition temperature of a binder resin which is an essential constituent of toner constituents. However, when trying to decrease the softening temperature and the glass transition temperature of the binder resin, since preservation stability of the toner decreases accordingly, fusion and adhesion of the toner easily occur in the standstill state at a high temperature and the high-stress state in a cartridge.
In order to solve the problem, it is necessary to maintain preservation stability of toner particles including a binder resin whose flow tester softening temperature and glass transition temperature are low. Thus, there is proposed an encapsulated toner in which toner base particles are coated with a coating layer having high flow tester softening temperature and glass transition temperature.
For example, Japanese Unexamined Patent Publication JP-A 2000-147829 discloses microcapsule toner particles achieving both low temperature fixation and preservation stability, which is constituted of a core material including a binder resin having a glass transition temperature of from −20 to 60° C. and an outer shell material including a binder resin having a glass transition temperature of from 60 to 180° C.
However, since the toner of the JP-A 2000-147829 uses resin having low glass transition temperature as a core material, when stacked printed matters are left under a high temperature environment such as in an automobile subjected to direct sunlight or when printed matters are discharged and stacked on a discharge tray, there poses a problem that a toner image is fused and adhered so that printed matters are adhered to each other. In order to avoid the problem, when resin having high glass transition temperature is used as the toner base particles serving as the core material, there poses a problem that it is impossible to enhance low temperature fixation property.